U.S. patent number 8,993,914 [Application Number 14/221,410] was granted by the patent office on 2015-03-31 for high-speed, high-resolution, triangulation-based, 3-d method and system for inspecting manufactured parts and sorting the inspected parts.
This patent grant is currently assigned to GII Acquisition, LLC. The grantee listed for this patent is GII Acquisition, LLC. Invention is credited to Nathan Andrew-Paul Kujacznski, Michael G. Nygaard.
United States Patent |
8,993,914 |
Kujacznski , et al. |
March 31, 2015 |
High-speed, high-resolution, triangulation-based, 3-D method and
system for inspecting manufactured parts and sorting the inspected
parts
Abstract
A high-speed, high-resolution, triangulation-based, 3-D method
and system for inspecting manufactured parts and sorting the
inspected parts are provided. The method includes consecutively
transferring the parts so that the parts move along a path which
extends from a supply of parts and through an imaging station. A
triangulation-based sensor head is supported at the imaging
station. The sensor head is configured to generate focused lines of
radiation and to sense corresponding reflected lines of radiation.
The focused lines are delivered onto an end surface of each part to
obtain a corresponding array of reflected lines of radiation. The
sensor head senses the array of reflected lines to obtain a
corresponding set of 2-D profile signals. The set of profile
signals represent a 3-D view of the end surface. The set of 2-D
profile signals of each part is processed to identify parts having
an unacceptable defect.
Inventors: |
Kujacznski; Nathan Andrew-Paul
(Flint, MI), Nygaard; Michael G. (Fenton, MI) |
Applicant: |
Name |
City |
State |
Country |
Type |
GII Acquisition, LLC |
Davisburg |
MI |
US |
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Assignee: |
GII Acquisition, LLC
(Davisburg, MI)
|
Family
ID: |
51934666 |
Appl.
No.: |
14/221,410 |
Filed: |
March 21, 2014 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140346095 A1 |
Nov 27, 2014 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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13901868 |
May 24, 2013 |
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Current U.S.
Class: |
209/576; 356/602;
209/587; 209/588; 209/589; 209/579; 345/49; 209/577;
250/559.23 |
Current CPC
Class: |
B07C
5/34 (20130101); B07C 5/342 (20130101) |
Current International
Class: |
B07C
5/00 (20060101) |
Field of
Search: |
;209/576,577,587,588,589
;345/49 ;356/602 ;250/559.23 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2005022076 |
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Mar 2005 |
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WO |
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2009130062 |
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Oct 2009 |
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WO |
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Other References
International Search Report and Written Opinion; International
application No. PCT/US2014/018663; date of mailing May 28, 2014.
cited by applicant.
|
Primary Examiner: Matthews; Terrell
Attorney, Agent or Firm: Brooks Kushman P.C.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. patent
application entitled "High-Speed, Triangulation-Based, 3-D Method
and System for Inspecting Manufactured Parts and Sorting the
Inspected Parts" filed on May 24, 2013 and having U.S. Ser. No.
13/901,868. This application is related to U.S. patent application
Ser. No. 13/714,999 filed on Dec. 14, 2012 and Ser. No. 13/901,862
filed on May 24, 2013.
Claims
What is claimed is:
1. A high-speed, high-resolution, triangulation-based, 3-D method
of inspecting manufactured parts and sorting the inspected parts,
the method comprising; receiving a supply of parts; consecutively
transferring the parts so that the parts move along a path which
extends from the supply of parts and through an imaging station;
supporting a triangulation-based sensor head at the imaging
station, the sensor head being configured to generate focused lines
of radiation and to sense corresponding reflected lines of
radiation; delivering the focused lines onto an end surface of each
part during motion of the parts relative to the focused lines to
obtain a corresponding array of reflected lines of radiation, the
sensor head sensing the array of reflected lines to obtain a
corresponding set of 2-D profile signals, the set of profile
signals representing a 3-D view of the end surface; processing the
set of 2-D profile signals of each part to identify parts having an
unacceptable defect; directing parts identified as having an
unacceptable defect to a defective part area; and directing parts
not identified as having an unacceptable defect to an acceptable
part area.
2. The method as claimed in claim 1, further comprising generating
control signals to control the sensor head based on the step of
transferring.
3. The method as claimed in claim 1, wherein the sensor head
includes at least one semiconductor laser.
4. The method as claimed in claim 1, wherein the focused lines of
radiation are polarized laser lines of light.
5. The method as claimed in claim 1, wherein the step of processing
determines a part parameter.
6. The method as claimed in claim 2, wherein the path is circular
and wherein the step of generating is performed with a rotary
encoder.
7. The method as claimed in claim 2, wherein the path is linear and
wherein the step of generating is performed with a linear
encoder.
8. The method as claimed in claim 1, further comprising the step of
coordinating the imaging of the parts at the imaging station with
the movement of the parts to and from the imaging station to
control the movement and the imaging of the parts.
9. The method as claimed in claim 6, wherein the step of
transferring is at least partially performed with a rotary glass
disk or table.
10. The method as claimed in claim 7, wherein the step of
transferring is at least partially performed with a track having an
elongated slit dimensioned to allow the focused and reflected lines
of radiation to pass therethrough.
11. A high-speed, high-resolution, triangulation-based, 3-D system
for inspecting manufactured parts and sorting the inspected parts,
the system comprising; a source of parts; a transfer subsystem for
consecutively transferring the parts from the source of parts so
that the parts move along a path which extends from the source of
parts and through an imaging station; a triangulation-based sensor
head located at the imaging station, the sensor head being
configured to generate focused lines of radiation and to sense
corresponding reflected lines of radiation, the sensor head
delivering the focused lines onto an end surface of each part
during motion of the parts relative to the focused lines to obtain
a corresponding array of reflected lines of radiation, the sensor
head sensing the array of reflected lines to obtain a corresponding
set of 2-D profile signals, the set of profile signals representing
a 3-D view of the end surface; at least one processor to process
the set of 2-D profile signals of each part to identify parts
having an unacceptable defect; a mechanism including a part sorter
for directing parts identified as having an unacceptable defect to
a defective part area, and directing parts not identified as having
an unacceptable defect to an acceptable part area; and a system
controller coupled to the at least one processor and the part
sorter to control the sorting based on the inspecting.
12. The system as claimed in claim 11, further comprising a sensor
for providing a control signal at each of a plurality of known
intervals of movement of the transfer subsystem, the control
signals being utilized to control the sensor head.
13. The system as claimed in claim 11, wherein the sensor head
includes at least one semiconductor laser.
14. The system as claimed in claim 11, wherein the focused lines of
radiation are polarized laser lines of light.
15. The system as claimed in claim 11, wherein the at least one
processor determines a part parameter.
16. The system as claimed in claim 12, wherein the path is circular
and wherein the sensor is a rotary sensor.
17. The system as claimed in claim 12, wherein the path is linear
and wherein the sensor is a linear sensor.
18. The system as claimed in claim 11, wherein the system
controller coordinates the imaging of the parts at the imaging
station with the movement of the parts to and from the imaging
station to control the movement and the imaging of the parts.
19. The system as claimed in claim 16, wherein the transfer
subsystem includes a rotary glass disk or table.
20. The system as claimed in claim 17, wherein the transfer
subsystem includes a track having an elongated slit dimensioned to
allow the focused and reflected lines of radiation to pass
therethrough.
Description
TECHNICAL FIELD
This invention relates, in general, to the field of non-contact,
optical inspection and sorting of parts, and, more particularly, to
triangulation-based, 3-D methods and systems for optically
inspecting and sorting manufactured parts.
OVERVIEW
Traditional manual, gauging devices and techniques have been
replaced to some extent by automatic inspection methods and
systems. However, such automatic inspection methods and systems
still have a number of shortcomings associated with them.
Many parts, such as valve spring retainers, rivets, washers, first
draw caps for ammunition, nuts, valve seats and the like develop
microscopic surface defects such as slight hollows or depressions
made in hard even surfaces by a blow or pressure during the
manufacturing process.
Jackets are traditionally produced in cup and draw operations. A
shallow cup is formed from a sheet of metal in a cupping press.
Dies and punches in the press blank out a disk of the sheet metal
and simultaneously form it into a shallow cup. The basic
requirements for cups are concentric wall thickness and relatively
even tops. The jacket is ultimately trimmed to meet
specifications.
A jacket that is not much taller than it is wide (some handgun
bullets) can often be used directly from the cupping press if the
initial sheet material's thickness is close to the desired jacket
thickness. For rifle bullets where the jacket can be two or more
times the diameter of the bullet in length, the cup must receive
additional processing. This is performed by the draw operation.
In metalworking, drawing a part refers to stretching it under
controlled conditions, while reducing the diameter. The control is
provided by a die and punch set that maintains constant contact
with the jacket walls, ensuring equal stresses at all points on the
bullet and controlling concentricity. The draw operation targets
the sidewalls of the cup. The resulting part looks like a metal
test tube, with a rounded base.
In drawing, several dies may be used in conjunction with one punch.
This progressive draw tooling is known as a die stack. The tooling
designer must consider the reduction in wall thickness and diameter
that the stack must produce. All the dies and the punch must make
full contact with the jacket so that no unworked metal remains when
the part exits the die stack.
In optical metrology, inter-reflection (i.e., double bounce or
secondary reflection) poses a challenge for surface measurement of
shiny objects. Due to specular reflections that can occur among
concave surfaces or combinations of surfaces positioned near right
angles to each other, the true desired laser lines are often
obscured by inter-reflection lines. Such obscuration makes it
difficult to measure shiny surfaces of complex surface
geometry.
Some laser triangulation measuring equipment operates by
projecting, with a laser beam having a wavelength centered at
approximately 830 nm (infrared (IR) radiation), a light spot having
a preset spot size onto the surface to be examined, e.g., from a
laser projection "gun" that may be mounted normal to the surface
being examined. A light detection unit including a lens and a light
detecting element or "camera," such as a CCD or CMOS imaging chip
or a position sensing device (PSD), e.g., of silicon, at an offset
angle to the projection axis may observe the position of the laser
spot in its field of view and output a signal describing the angle
at which the spot appeared in the field of view. The range to the
object can be computed from the angle information when the distance
between the laser projection axis and the light detection unit is
known. The offset angle between the laser beam and the line of
sight of the light detection unit is often referred to as the
"triangulation angle." Based on which part of the detector the
light reflected from the imaged object impinges, the height or
"z-component" of the object at the point at which the light spot
impinges upon the object may be determined.
U.S. Pat. No. 7,403,872 discloses a method and system for
inspecting manufactured parts such as cartridges and cartridge
cases and sorting the inspected parts.
WO 2005/022076 discloses a plurality of light line generators which
generate associated beams of light that intersect a part to be
inspected.
U.S. Pat. No. 6,313,948 discloses an optical beam shaper for
production of a uniform sheet of light for use in a parts
inspection system having a light source including a coherent light
generator, a diffractive beam shaper, and lens elements.
U.S. Pat. No. 6,285,034 discloses an inspection system for
evaluating rotationally asymmetric workpieces for conformance to
configuration criteria.
U.S. Pat. No. 6,252,661 discloses an inspection system for
evaluating workpieces for conformance to configuration
criteria.
U.S. Pat. No. 6,959,108 discloses an inspection system wherein
workpieces to be inspected are consecutively and automatically
launched to pass unsupported through the field of view of a
plurality of cameras.
U.S. Pat. No. 4,831,251 discloses an optical device for
discriminating threaded workpiece by the handedness by their screw
thread profiles.
U.S. Pat. No. 5,383,021 discloses a non-contact inspection system
capable of evaluating spatial form parameters of a workpiece to
provide inspection of parts in production.
U.S. Pat. No. 5,568,263 also discloses a non-contact inspection
system capable of evaluating spatial form parameters of a workpiece
to provide inspection of parts in production.
U.S. Pat. No. 4,852,983 discloses an optical system which simulates
the optical effect of traveling over a large distance on light
traveling between reference surfaces.
U.S. Patent Application Publication No. 2005/0174567 discloses a
system to determine the presence of cracks in parts.
U.S. Patent Application Publication No. 2006/0236792 discloses an
inspection station for a workpiece including a conveyor, a
mechanism for rotating the workpiece, and a probe.
U.S. Pat. No. 6,289,600 discloses a non-contact measuring device
for determining the dimensions of a cylindrical object, such as a
pipe.
U.S. Pat. No. 5,521,707 discloses a non-contact laser-based sensor
guided by a precision mechanical system to scan a thread form
producing a set of digitized images of the thread form.
WO 2009/130062 discloses a method and a device for the optical
viewing of objects.
As described in U.S. Pat. No. 6,098,031, triangulation is the most
commonly used 3-D imaging method and offers a good figure of merit
for resolution and speed. U.S. Pat. Nos. 5,024,529 and 5,546,189
describe the use of triangulation-based systems for inspection of
many industrial parts, including shiny surfaces like pins of a grid
array. U.S. Pat. No. 5,617,209 shows a scanning method for grid
arrays which has additional benefits for improving accuracy. The
method of using an angled beam of radiant energy can be used for
triangulation, confocal or general line scan systems.
Unfortunately, triangulation systems are not immune to fundamental
limitations like occlusion and sensitivity to background
reflection. Furthermore, at high magnification, the depth of focus
can limit performance of systems, particularly edge location
accuracy, when the object has substantial relief and a wide dynamic
range (i.e. variation in surface reflectance). In some cases,
camera-based systems have been combined with triangulation systems
to enhance measurement capability.
U.S. Pat. No. 5,098,031 discloses a method and system for
high-speed, 3-D imaging of microscopic targets. The system includes
confocal and triangulation-based scanners or subsystems which
provide data which is both acquired and processed under the control
of a control algorithm to obtain information such as dimensional
information about the microscopic targets which may be
"non-cooperative." The "non-cooperative" targets are illuminated
with a scanning beam of electromagnetic radiation such as laser
light incident from a first direction. A confocal detector of the
electromagnetic radiation is placed at a first location for
receiving reflected radiation which is substantially optically
collinear with the incident beam of electromagnetic radiation. The
triangulation-based subsystem also includes a detector of
electromagnetic radiation which is placed at a second location
which is non-collinear with respect to the incident beam. Digital
data is derived from signals produced by the detectors.
U.S. Pat. No. 5,815,275 discloses triangulation-based 3-D imaging
using an angled scanning beam of radiant energy.
U.S. Pat. Nos. 7,812,970 and 7,920,278 disclose part inspection
using a profile inspection subsystem and triangulation.
U.S. Pat. No. 4,547,674 discloses a method and apparatus for
inspecting gear geometry via optical triangulation.
U.S. Pat. No. 4,970,401 discloses a non-contact triangulation probe
system including a base plate and a first non-contact triangulation
probe including a light source mounted on a first movable
slide.
U.S. Pat. Nos. 5,168,458 and 5,170,306 disclose methods and systems
for gauging threaded fasteners to obtain trilobular parameters.
Other U.S. patent documents related to the invention include: U.S.
Pat. Nos. 4,315,688; 4,598,998; 4,644,394; 4,852,983; 4,906,098;
5,521,707; 5,608,530; 5,646,724; 5,291,272; 6,055,329; 4,983,043;
3,924,953; 5,164,995; 4,721,388; 4,969,746; 5,012,117; 7,684,054;
7,403,872; 7,633,635; 7,312,607, 7,777,900; 7,633,046; 7,633,634;
7,738,121; 7,755,754; 7,738,088; 7,796,278; 7,684,054; 8,054,460;
8,179,434; 8,416,403 and U.S. published patent applications
2010/0245850, 2010/0201806, 2012/0293623; and 2012/0293789.
SUMMARY OF EXAMPLE EMBODIMENTS
An object of at least one embodiment of the present invention is to
provide a high-speed, high-resolution, triangulation-based, 3-D
method and system for precisely inspecting the end surfaces of
manufactured parts and sorting the inspected parts at a relatively
low cost.
In carrying out the above object and other objects of at least one
embodiment of the present invention, a high-speed, high-resolution,
triangulation-based, 3-D method of inspecting manufactured parts
and sorting the inspected parts is provided. The method includes
receiving a supply of parts and consecutively transferring the
parts so that the parts move along a path which extends from the
supply of parts and through an imaging station. The method also
includes supporting a triangulation-based sensor head at the
imaging station. The sensor head is configured to generate focused
lines of radiation and to sense corresponding reflected lines of
radiation. Further, the method includes delivering the focused
lines onto an end surface of each part during motion of the parts
relative to the focused lines to obtain a corresponding array of
reflected lines of radiation. The sensor head senses the array of
reflected lines to obtain a corresponding set of 2-D profile
signals. The set of profile signals represent a 3-D view of the end
surface. The method further includes processing the set of 2-D
profile signals of each part to identify parts having an
unacceptable defect, directing parts identified as having an
unacceptable defect to a defective part area and directing parts
not identified as having an unacceptable defect to an acceptable
part area.
The method may further include generating control signals to
control the sensor head based on the step of transferring.
The sensor head may include at least one semiconductor laser.
The focused lines of radiation may be polarized laser lines of
light.
The step of processing may determine a part parameter.
The path may be circular wherein the step of generating is
performed with a rotary encoder.
The path may be linear wherein the step of generating is performed
with a linear encoder.
The method may further include the step of coordinating the imaging
of the parts at the imaging station with the movement of the parts
to and from the imaging station to control the movement and the
imaging of the parts.
The step of transferring may be at least partially performed with a
rotary glass disk or table.
The step of transferring may be at least partially performed with a
track having an elongated slit dimensioned to allow the focused and
reflected lines of radiation to pass therethrough.
Further, in carrying out the above object and other objects of at
least one embodiment of the present invention, a high-speed,
high-resolution, triangulation-based, 3-D system for inspecting
manufactured parts and sorting the inspected parts is provided. The
system includes a source of parts and a transfer subsystem for
consecutively transferring the parts from the source of parts so
that the parts move along a path which extends from the source of
parts and through an imaging station. The system also includes a
triangulation-based sensor head located at the imaging station. The
sensor head is configured to generate focused lines of radiation
and to sense corresponding reflected lines of radiation. The sensor
head delivers the focused lines onto an end surface of each part
during motion of the parts relative to the focused lines to obtain
a corresponding array of reflected lines of radiation. The sensor
head senses the array of reflected lines to obtain a corresponding
set of 2-D profile signals. The set of profile signals represent a
3-D view of the end surface. The system also includes at least one
processor to process the set of 2-D profile signals of each part to
identify parts having an unacceptable defect. A mechanism including
a part sorter is provided for directing parts identified as having
an unacceptable defect to a defective part area and directing parts
not identified as having an unacceptable defect to an acceptable
part area. A system controller coupled to the at least one
processor and the part sorter controls the sorting based on the
inspecting.
The system may further include a sensor for providing a control
signal at each of a plurality of known intervals of movement of the
transfer subsystem. The control signals are utilized to control the
sensor head.
The sensor head may include at least one semiconductor laser.
The focused lines of radiation may be polarized laser lines of
light.
The at least one processor may determine a part parameter.
The path may be circular wherein the sensor is a rotary sensor.
The path may be linear wherein the sensor is a linear sensor.
The system controller may coordinate the imaging of the parts at
the imaging station with the movement of the parts to and from the
imaging station to control the movement and the imaging of the
parts.
The transfer subsystem may include a rotary glass disk or
table.
The transfer subsystem may include a track having an elongated slit
dimensioned to allow the focused and reflected lines of radiation
to pass therethrough.
Other technical advantages will be readily apparent to one skilled
in the art from the following figures, descriptions and claims.
Moreover, while specific advantages have been enumerated, various
embodiments may include all, some or none of the enumerated
advantages.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic perspective view of a system constructed in
accordance with at least one embodiment of the present
invention;
FIG. 2 is a front view of the system of FIG. 1;
FIG. 3 is a side view of the system of FIG. 1;
FIG. 4 is a view taken along lines 4-4 of FIG. 2 illustrating
various possible stations, including an imaging station, located
about a rotary glass disk or table of the system;
FIG. 5 is a side view of a part such as a first draw cup for
ammunition supported on the disk or table of FIG. 4;
FIG. 6 is a schematic block diagram of the system of FIG. 1
including a top imaging station with a control system;
FIG. 7 is a schematic block diagram of the system of FIG. 1 at a
bottom imaging station with the control system of FIG. 6;
FIG. 8 is an image which shows a part with a surface defect (i.e. a
dent) next to a photo realistic view of the part;
FIG. 9 is an image and view similar to the image and view,
respectively, of FIG. 8 wherein the data is "zoomed in" to make the
surface defect easier to see; and
FIG. 10 is a block diagram flow chart illustrating a high-speed,
high-resolution, triangulation-based, 3-D method of optically
inspecting and sorting the inspected manufactured parts in
accordance with at least one embodiment of the invention.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
As required, detailed embodiments of the present invention are
disclosed herein; however, it is to be understood that the
disclosed embodiments are merely exemplary of the invention that
may be embodied in various and alternative forms. The figures are
not necessarily to scale; some features may be exaggerated or
minimized to show details of particular components. Therefore,
specific structural and functional details disclosed herein are not
to be interpreted as limiting, but merely as a representative basis
for teaching one skilled in the art to variously employ the present
invention.
In general, and as described below, at least one embodiment of the
present invention provides a high-speed, high-resolution
triangulation-based, 3-D method and system for inspecting
manufactured parts at one or more imaging stations and sorting the
inspected parts. The parts, such as valve seats, washers, valve
spring retainers, nuts, first draw caps for ammunition and rivets
have top and bottom end surfaces which are optically inspected.
In general, one embodiment of the high-speed, high-resolution,
triangulation-based, 3-D method and system of the present invention
optically inspects manufactured parts such as the parts illustrated
in FIGS. 4 through 9. The inspected parts are then typically sorted
based on the inspection(s). The system, generally indicated at 10,
is designed for the inspection of one or more outer end surfaces of
the parts. The system 10 is suitable for the inspection of small,
mass-produced manufactured parts. The subsystems of the system 10
which may be used for part handling and delivery may vary widely
from application to application depending on part size and shape,
as well as what inspections are being conducted. The subsystems
ultimately chosen for part handling and delivery have some bearing
on the nature of the subsystems conducting the optical and other
non-contact inspection.
Initially, parts, such as first drawn caps 11 (FIGS. 4-7) or valve
spring retainers 13 (FIGS. 8-9) are placed into a source of parts
such as an orienting feeder bowl 12 having a scalloped rim 14. The
bowl 12 is supported on an adjustable frame structure 16. Tooling
around the rim 14 takes advantage of the asymmetrical mass
distribution of the parts to feed the parts onto a
downwardly-sloped feeder conveyor or loader 18. Consequently, every
part which exits the bowl 12 is received by the conveyor 18 and is
properly oriented. One or more vibrators (not shown) controlled by
a vibrator controller (not shown) vibrate the bowl 12 to help move
the parts in single file to a loading station.
The system 10 typically includes a part transfer subsystem
including a transfer mechanism, generally indicated at 30 in FIG.
6, and/or a transfer mechanism, generally indicated at 40 in FIG.
7. Each mechanism 30 or 40 is adapted to receive and retain parts
thereon at a loading station at which a loader loads parts to be
inspected from the bowl 12 or other storage or transfer device. The
transfer mechanism 40 may include a slotted, flat track 41 on which
the parts 11 are conveyed at a bottom imaging station. The bottom
imaging station typically includes a conveyor 42 or some linear
motion "pusher" type actuator having a linear encoder coupled to
the conveyor 42 to generate encoder signals and supply such signals
to a sensor head 46 and to the system controller. A slot 43 of the
track 41 is dimensioned to allow focused and reflected lines of
radiation to pass therethrough but not allow the parts 11 to fall
therethrough as described hereinbelow. The conveyor 42 may be a
magnetic or vacuum conveyor for transferring parts to the transfer
mechanism 30. Magnetic conveyors are frequently used to convey
ferromagnetic articles, such as cans, stampings and the like. In
conveyors of this type, permanent magnets are located in the frame
of the conveyor beneath the conveying run of an endless belt and
articles are attracted to the magnets so that the belt can travel
along an incline or horizontal or vertical path of travel without
the articles falling from the belt.
Alternatively, an indexing, beltless magnetic conveyor may be
provided. Such a conveyor may include a housing defining a
longitudinal length of the conveyor and a magnetic rack assembly
moveably supported in the housing. The magnetic rack assembly
includes a plurality of magnet assemblies supported at spaced
intervals relative to one another along the longitudinal length of
the conveyor. The beltless magnetic conveyor also includes a drive
which is controlled by the system controller to index the magnetic
rack assembly between a home or loading position proximate to one
end of the housing and an end or inspection position which is
proximate to an opposite end of the housing over the same path. The
magnet assemblies are operable to generate a magnetic force which
acts to attract ferromagnetic material toward the housing and to
move the ferromagnetic material in the direction of the
longitudinal length of the conveyor when the magnetic rack assembly
is indexed.
The transfer mechanism 30 may be a rotating glass table or disk as
shown in FIG. 6 to transfer the retained parts so that the parts
travel along a first path which extends from a loader at a loading
station to a top inspection or imaging station at which the parts
have a predetermined position and orientation for optical
inspection. Subsequently, the transfer mechanism 30 transfers the
parts after imaging at the imaging station so that the inspected
parts travel along a second path which extends from the imaging
station to an unloader at an unloading station at which the
inspected parts are unloaded from the transfer mechanism 30 by the
unloader. The loader and unloader may be the same device, which can
place parts which "pass" the inspection in a "good part" bin 33 and
place parts which don't "pass" the inspection in a `defective part"
bin 34. The unloading station may be coincident with the loading
station and the loading and unloading may be done manually or
automatically.
The movable table or disk 30 may be a rotary index table or disk,
for transferring parts at the top surfaces of the table 30. The
table 30 is coupled to a rotary sensor or encoder which provides a
control or encoder signal to the system controller and to a sensor
head substantially identical to the sensor head 46 at the top
imaging station at each of a plurality of known intervals of
movement of the table 30. The control signals are utilized by the
sensor head at the top imaging station as described hereinbelow.
The rotary index table 30 typically has a central rotational axis
35 and an outer periphery which has a round shape. A rotary drive
of the table 30 operates to rotate the index table 30 on a base for
indexing rotation about the rotational axis 34 based on various
sensor input signals from sensors to the system controller which,
in turn, provides sequential control signals to a positioning drive
mechanically coupled to the rotary drive. The system controller
also provides control signals to a computer display and a part
sorter or reject mechanism (for example, a solenoid-operated
diverter or flipper 32 of FIG. 7). The rotary drive drives the
index table 30 between inspection stations such as machine vision
and eddy current stations.
The parts may be dropped onto the track 41 from the track 18. As
the parts 11 move down and exit the track 41, they pass through the
bottom imaging station to be inspected one at a time. The parts 11
which fail the inspection may be actively rejected by the part
diverter or flipper 32. Parts which pass the inspection at the
bottom imaging station are transferred to the rotary table 30 for
top inspection.
A sensor head such as the sensor head 46 is located in both the top
and bottom inspection stations. The sensor head is preferably a
triangulation-based sensor head 46 supported and mounted within
each of the top and bottom imaging stations. Each sensor head 46
illuminates either a top or bottom surface of each part 11 with
focused planes or lines of radiation to obtain corresponding
reflected lines when the part 11 is in the imaging station. The
sensor heads 46 sense their corresponding reflected lines to obtain
corresponding 2-D profile signals.
As the parts 11 move through the imaging stations, corresponding
sets of 2-D profile signals are generated by the sensor heads 46.
At least one processor processes the sets of 2-D profile signals to
obtain a 3-D view of each top or bottom surface of the part 11.
The system controller provides control signals based on the signals
from the linear and rotary sensors or encoders. Alternatively or
additionally, the signals from the rotary and linear encoders are
directly utilized by the sensor heads 46 at the top and bottom
vision stations to control the sensor heads 46. The control signals
are utilized to control the sensor heads 46 which preferably have
encoder inputs which allow precise control over the position of 2-D
profile signals samples.
At least one signal processor may process the sets of 2-D profile
signals to identify a defective part as described in greater detail
hereinbelow. The at least one processor may process the sets of 2-D
profile signals to obtain one or more measurements of the part.
Each of the sensor heads 46 may comprise a high-speed, 2D/3D laser
scanner (LJ-V7000 series) available from Keyence Corporation of
Japan. Such a sensor head from Keyence generates a laser beam that
has been expanded into a line and is reflected from the surface of
the part. This reflected line of light is formed on a HSE3-CMOS
sensor and by detecting changes in the position and shape of the
reflection, it is possible to measure the position of various
points along the surface of the part.
Such a sensor head 46 typically includes a cylindrical lens, at
least one and preferably two semiconductor laser diodes, a
GP64-Processor, a 2D Ernostar lens and a HSE3-CMOS sensor.
Preferably, the laser diodes emit "blue" light beams which are
polarized and combined by optical elements or components to form
the line of laser light.
Preferably, the beams from the pair of blue laser diodes are
combined such that the transmitted beam is polarized in both X and
Y axes. The captured images at the sensor in both polarizations are
used to generate a resulting 2-D profile signal wherein stray
reflections are cancelled.
A comparison of such sensor heads 46 with 3-D measurement cameras
reveal the following:
1. Easy Installation
When using a 3D camera, the laser light source and receiver
(camera) are independent of each other, greatly complicating
on-site installation and adjustment. With such sensor heads 46, the
laser light source and receiver are contained in a single body or
enclosure, making transmitter-to-receiver mounting adjustment
unnecessary. This also ensures that the transmitter and receiver
maintain this alignment regardless of machine use.
2. No Linearization Required
When using a 3D camera, the height of individual pixels and pixel
pitch vary due to the relative positions of the laser light source
and the receiver, requiring on-site linearization following
installation. With such sensor heads 46, the output data is
pre-linearized by the on-board controller (not shown) of the sensor
head 46 without the need for additional post-processing.
3. Out of the Box Traceability
Because each such sensor head 46 is not a machine vision camera,
but a traceable measurement device, traceability and calibration
documentation is available out of the box. All such devices are
factory calibrated to international traceability standards and
compliance documentation is readily available.
The 2-D profile signals may be pre-processed by the on-board
processor of the sensor head 46 and then processed by the at least
one signal processor under system control to obtain a view or image
which is used by the processor to determine at least one of a dent,
a split, a perforation, a crack, a scratch, a wrinkle, a buckle, a
bulge, and a surface blemish located at the end surfaces of the
part.
The system 10 is an integrated system designed to fully inspect and
measure parts at their ends at the top and bottom imaging stations.
The system 10 can inspect parts which are supported on a track such
as the track 41 which has the narrow slit 43 formed therein to
allow an unobstructed view of the bottom end surface of the part
11.
FIG. 10 is a detailed block diagram flow chart describing a method
of at least one embodiment of the present invention, generally
indicated at 100, as follows:
1. Receive a supply of parts such as ammunition caps (block
102);
2. Consecutively transfer the parts so that the parts move along a
path including an imaging station (block 104);
3. Support a triangulation-based sensor head 46 at the imaging
station (block 106);
4. Deliver focused lines of radiation generated by the sensor head
46 to an exterior end surface (i.e. top or bottom) of the moving
part and sense arrays of the reflected lines of radiation to obtain
a set of 2-D profile signals (block 108);
5. Process the set of 2-D profile signals (block 110);
6. Determine a part parameter or property using the set of 2-D
profile signals (block 112);
7. Is part parameter or property within a range of acceptable
values? (block 114);
8. If block 114 is "yes" accept part (block 116); and
9. If block 114 is "no" reject part as being defective (block
118).
A "reject mechanism" or unloader in the inspection and sorting
system can be implemented in a number of equivalent known
embodiments. For example, a "reject mechanism" could remove a
nonconforming workpiece in a number of ways, by (i) routing the
workpiece on a conveyor to a bin for nonconforming parts, (ii)
mechanically displacing the workpiece from a conveyor into a bin,
such as by a flipper or pusher device, (iii) magnetically
displacing a (ferrous) workpiece by selective actuation of a
magnet, (iv) pneumatically displacing the workpiece into a bin,
such as by pressurized air, (v) using a robotic arm to pick up and
remove the nonconforming workpiece, among other equivalent
ways.
For example, a wide variety of reject mechanisms or reject gates
are possible. The same gate can be used mechanically but software
can be configured to allow the gate to be "RZ--return to zero" or
"NRZ--non return to zero" modes. In RZ mode, the gate would stay
shut and only open for good parts, then would return to zero for
the good part signal. In NRZ mode the gate stays open and waits for
the reject part signal, then would shut (return to zero) to reject
the part, then open back up to wait for the next reject signal. In
this way, the customer can choose which configuration to use. The
dial table sorting machine can have multiple sensors that determine
whether the part is accepted or rejected. The good parts are blown
off into a good chute first. Then, the remaining parts are rejected
by a wiper that simply stops the parts from continuing around the
dial table, as the rejected part is wiped into the reject bin. Or,
the customer can select the opposite, blow the reject parts off and
allow the wiper to collect good parts.
One or More Signal Processors for the Detection of Surface Defects
on Small Manufactured Parts
The system 10 is especially designed for the inspection of
relatively small manufactured parts. The processing of images
and/or signals of the parts to detect defective parts begins after
the sensor head 46 or probe projects a line of laser light onto the
surface while the sensor camera continuously records the changing
distance and shape of the laser line in three dimensions (XYZ) as
it sweeps along the object.
Referring now to FIGS. 8 and 9, the shape of the object or part
appears as millions of points called a "point cloud" on the
computer monitor as the laser moves around capturing the entire end
surface shape of the object. The process is very fast, gathering up
to 750,000 points per second and very precise (to .+-.0.0005'').
After the huge point cloud data files are created, they are
registered and merged into one three-dimensional representation of
the object and post-processed with various software packages
suitable for the specific application. The scanned object can be
compared to the designer's CAD nominal data. The result of this
comparison process is delivered in the form of a "color map
deviation report," which pictorially describes the differences
between the scan data and the CAD data.
The image of FIG. 8 shows a part with a dent defect and what that
defect looks like to the topography sensor head 46. The image of
FIG. 9 shows how one can zoom in on the data from the topography
sensor head 46 to make the dent defects easier to see.
While exemplary embodiments are described above, it is not intended
that these embodiments describe all possible forms of the
invention. Rather, the words used in the specification are words of
description rather than limitation, and it is understood that
various changes may be made without departing from the spirit and
scope of the invention. Additionally, the features of various
implementing embodiments may be combined to form further
embodiments of the invention.
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